Every year, from March 8 to 14, World Glaucoma Week mobilizes healthcare professionals and patient organizations to raise awareness of this silent eye disease. Glaucoma is the second leading cause of blindness worldwide, after cataracts - and unlike cataracts, blindness caused by glaucoma is irreversible. What makes this disease particularly fearsome is its asymptomatic nature over many years: vision gradually deteriorates, starting in the periphery, without pain or warning, until irreparable damage to the optic nerve has already occurred.
In Canada, it is estimated that over 700,000 people suffer from glaucoma, and up to half of them are unaware of it. Early detection is the only effective strategy for preventing glaucoma-related blindness. Clinique Omicron offers screening ophthalmological assessments at several of its branches in Quebec.
What is glaucoma and how does it damage vision?
Glaucoma refers to a group of eye diseases that share a common characteristic: progressive destruction of the optic nerve, the nerve cable that transmits visual information from the eye to the brain. In the vast majority of cases, this destruction is linked to excessively high intraocular pressure (IOP) - although there are forms of normal-pressure glaucoma where other mechanisms are involved. Aqueous humor, a liquid produced inside the eye, circulates normally and drains through a trabecular network. When this drainage is insufficient, pressure builds up and compresses the optic nerve.
Optic nerve fibers do not regenerate. Once destroyed, they are gone for good. This is why glaucoma first causes a loss of peripheral vision - which the brain compensates for remarkably well, making the disease invisible in its early stages - before affecting central vision in the advanced stages. At this stage, visual loss is already significant and irreversible.
The different types of glaucoma
Open-angle glaucoma is the most common form, accounting for around 90 % of cases. It develops very slowly and without symptoms. Aqueous humor drainage becomes progressively less efficient, leading to a gradual increase in eye pressure. It is the form most often diagnosed late, due to its silent evolution. Angle-closure glaucoma is less common, but can manifest itself acutely - with intense pain, redness of the eye, blurred vision and nausea - constituting an ophthalmological emergency. It is more common in people of Asian origin and in women.
There is also congenital glaucoma, present from birth or appearing in early childhood, and secondary forms linked to other conditions such as diabetes, ocular hypertension or prolonged use of corticosteroids.
Risk factors: who's most vulnerable?
Age is the main risk factor: glaucoma is rare before the age of 40, but its prevalence increases sharply thereafter. After the age of 70, approximately one person in ten is affected. Family history is a major risk factor - having a parent or sibling with glaucoma multiplies personal risk by a factor of four to nine. High intraocular pressure - known as ocular hypertension - is the best-known modifiable risk factor, although some people develop glaucoma with normal pressure.
Other risk factors include high myopia, a thin cornea, a history of eye trauma, prolonged use of corticosteroid medications in any form - eye drops, inhalers, creams or tablets - as well as certain systemic diseases such as diabetes, hypertension and sleep apnea syndrome. People of African or Afro-Caribbean origin have a significantly higher risk of developing glaucoma, at a younger age and in a more aggressive form.
Diagnosis and screening: essential tests
Screening for glaucoma involves more than measuring eye pressure - although this is an important element. A complete examination includes tonometry to measure intraocular pressure, fundus examination to assess the appearance of the optic nerve, pachymetry to measure the thickness of the cornea - which influences the interpretation of the measured pressure - and the visual field to detect areas of peripheral visual loss. OCT - optical coherence tomography - enables a detailed analysis of the thickness of retinal nerve fiber layers, and can detect abnormalities even before visual loss is perceptible in the visual field.
A preventive visual check-up is recommended every two years from the age of 40, and more frequently in the presence of risk factors. An ophthalmological consultation or evaluation by an optometrist is the usual point of entry for this type of screening. Clinique Omicron offers basic visual assessments to identify patients requiring further investigation.
Treatment: slow progression, protect vision
There is no cure for glaucoma, but its progression can be effectively slowed or halted in the vast majority of cases if diagnosed early. First-line treatment consists of hypotensive eye drops - notably prostaglandins and beta-blockers - which reduce aqueous humor production or facilitate its drainage. These drops are generally taken daily for life. When drops are insufficient, laser surgery - trabeculoplasty or iridotomy - or filtering surgery may be considered. The aim is always to reduce eye pressure to a target level that will halt or slow optic nerve damage.
Frequently asked questions about glaucoma and vision screening in Quebec
Does glaucoma hurt?
Not in its most common form - chronic open-angle glaucoma. This is precisely what makes it such a dangerous disease: it progresses painlessly, without redness or visible symptoms, for years. Acute pain and symptoms are associated with acute angle-closure glaucoma, which is an ophthalmic emergency requiring immediate attention. If you experience intense eye pain accompanied by blurred vision and nausea, go to the emergency room without delay.
My vision is perfect - can I still get glaucoma?
Yes, that's right. This is one of the most deceptive aspects of glaucoma. Central vision - that used for reading and recognizing faces - is preserved until a very advanced stage of the disease. Loss of peripheral vision is compensated for by the brain so effectively that most patients don't notice a thing. Visual acuity of 10/10 is no guarantee of glaucoma absence. Only a complete ophthalmological examination, including optic nerve and visual field examination, can rule out the disease.
If my parent has glaucoma, at what age should I start screening?
If there's a family history of first-degree glaucoma, an initial comprehensive ophthalmological examination is recommended from the age of 35 to 40, and repeated every one to two years depending on the results. It's important not to wait until the usual age of 50 or 60, as hereditary glaucoma may appear earlier. Tell your doctor or optometrist about your family history, so that he or she can adjust the frequency of monitoring.
Should glaucoma drops be taken for life?
In most cases, yes. Glaucoma is a chronic disease, and hypotensive eye drops keep pressure at a safe level for as long as they are used - but do not act on the underlying cause of the disease. Stopping treatment allows the pressure to rise and progression to resume. Some patients may benefit from laser or filtering surgery, which reduces their dependence on drops, or even eliminates them for a time. The decision is taken in consultation with the ophthalmologist, depending on how the disease is progressing.
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